Method for operating a coriolis mass flowmeter and associated coriolis mass flowmeter

Abstract

A method for operating a Coriolis mass flowmeter having at least one measuring tube, at least one oscillation generator, at least one oscillation sensor and at least one strain sensor. The oscillation generator is actuated with an oscillation excitation signal and the measuring tube is excited to oscillation by the oscillation generator, the oscillation of the measuring tube is detected by the oscillation sensor and an oscillation sensor signal is generated. The strain sensor is mechanically coupled to the measuring tube via a connection. A change of the mechanical coupling via the connection can be determined by the oscillation of the measuring tube being measured by the strain sensor and a strain sensor signal generated representing oscillation of the measuring tube, a correlation between the strain sensor signal and an oscillation signal representing the oscillation of the measuring tube is identified, and a temporal change of the correlation is determined.

What is claimed is: 
     
       1. A method for operating a Coriolis mass flowmeter comprising:
 at least one measuring tube, 
 at least one oscillation generator, 
 at least one oscillation sensor and 
 at least one strain sensor, 
 wherein the oscillation generator is actuated with an oscillation excitation signal and the measuring tube is excited to oscillation by the oscillation generator, 
 wherein the oscillation of the measuring tube is detected by the at least one oscillation sensor and an oscillation sensor signal is generated, 
 wherein the strain sensor is mechanically coupled to the measuring tube via a connection, 
 wherein oscillation of the measuring tube is measured by the at least one strain sensor and a strain sensor signal is generated representing the oscillation of the measuring tube, 
 wherein a correlation between the strain sensor signal and an oscillation signal representing the oscillation of the measuring tube is identified, and 
 wherein a temporal change of the correlation is determined. 
 
     
     
       2. The method according to  claim 1 , wherein a decrease of the correlation with the passing of time is associated with a decrease in mechanical coupling via the connection. 
     
     
       3. The method according to  claim 1 , wherein at least one of the oscillation sensor signal and the oscillation excitation signal is used as the oscillation signal. 
     
     
       4. The method according to  claim 1 , wherein the oscillation signal is generated in a manner representative the speed of the oscillation of the measuring tube. 
     
     
       5. The method according to  claim 1 , wherein the correlation is identified by a transfer function between the oscillation signal and the strain sensor signal being determined. 
     
     
       6. The method according to  claim 1 , wherein the correlation is identified by a first amplitude of the oscillation of the measuring tube being determined from the strain sensor signal, a second amplitude of the oscillation of the measuring tube being determined from the oscillation signal, by the first amplitude and the second amplitude being set in relation to one another and a phase of the strain signal being determined in respect to the oscillation signal. 
     
     
       7. The method according to  claim 1 , wherein mechanical strains arising in the measuring tube are measured by the strain sensor and the measured mechanical strains are used for compensating for any effect of the mechanical strains on the oscillation sensor signals. 
     
     
       8. A Coriolis mass flowmeter comprising:
 at least one measuring tube, 
 at least one oscillation generator, 
 at least one oscillation sensor, 
 at least one strain sensor, and 
 an evaluation unit, 
 wherein the at least one oscillation generator is positioned so as to be able to excite the measuring tube to oscillation, 
 wherein the at least one oscillation sensor positioned so as to be able to detect oscillation of the measuring tube and to generate an oscillation sensor signal, 
 wherein the at least one strain sensor is mechanically coupled to the at least one measuring tube via a connection, 
 wherein the evaluation unit is adapted to generate an oscillation excitation signal and to actuate the oscillation generator with the oscillation excitation signal, 
 wherein the at least one strain sensor is adapted to measure oscillation of the measuring tube and to emit a strain sensor signal representing the oscillation of the measuring tube, and 
 wherein the evaluation unit is adapted to identify a correlation between the strain sensor signal and an oscillation signal representing the oscillation of the measuring tube and to determine a temporal change of the correlation. 
 
     
     
       9. The Coriolis mass flowmeter according to  claim 8 , wherein the evaluation unit is adapted to associate a decrease of the correlation with the passing of time with a decrease in the mechanical coupling via the connection. 
     
     
       10. The Coriolis mass flowmeter according to  claim 8 , wherein the strain sensor is arranged on the measuring tube via the connection. 
     
     
       11. The Coriolis mass flowmeter according to  claim 9 , wherein the connection comprises an adhesive bond. 
     
     
       12. The Coriolis mass flowmeter according to  claim 8 , wherein the strain sensor is a strain gauge.